1. Field of the Invention
The present invention relates to a substrate treatment apparatus for cleaning a substrate. Examples of the substrate to be cleaned include semiconductor wafers, substrates for liquid crystal display devices, substrates for plasma display devices, substrates for FED (Field Emission Display) devices, substrates for optical disks, substrates for magnetic disks, substrates for magneto-optical disks and substrates for photo masks.
2. Description of Related Art
In semiconductor device production processes, contamination of the periphery of a semiconductor wafer (hereinafter referred to simply as “wafer”) often significantly influences the treatment quality of the wafer. In a so-called batch treatment process, more specifically, a plurality of wafers are immersed in a vertical orientation in a treatment liquid. Therefore, if contaminants are present on the peripheries of the wafers, the contaminants are liable to be dispersed in the treatment liquid and adhere onto device formation regions of front surfaces of the wafers.
This leads to a recent increasing demand for techniques for cleaning the peripheries of the wafers and other types of substrates.
The following technique is proposed as a prior-art technique for cleaning the periphery of the substrate (see, for example, Japanese Unexamined Patent Publication No. 2006-278592). After the front surface of the substrate is cleaned with a chemical agent for removal of substances (contaminants), the chemical agent and the substances remaining on the front surface of the substrate are washed away by supplying pure water to a center portion of the front surface of the substrate. At this time, a peripheral surface of a cylindrical brush is brought into contact with the periphery of the substrate, whereby substances adhering to the periphery of the substrate are removed.
However, where the front surface of the substrate is hydrophobic (for example, where a low-k film is formed on the front surface of the substrate or where bare silicon is exposed on the front surface of the substrate), the supply of the pure water onto the center portion (device formation region) of the front surface may result in water marks (a trace of water remaining after drying) formed in the device formation region. Further, where copper interconnections or the like are provided on the front surface of the substrate, the supply of the pure water onto the center portion of the front surface of the substrate may result in corrosion of the copper interconnections due to oxidation.
One conceivable approach to this problem is to supply no pure water onto the front surface of the substrate. In this case, however, contaminants scraped from the periphery of the substrate by the brush remains on the periphery and, when the substrate is dried in this state, the contaminants adhere to the substrate.